NRF MME Identification for Inter-RAT Context Transfer
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Solution Overview
Problem
Current 3GPP standards lack efficient mechanisms for Mobility Management Entity (MME) identification in inter-Radio Access Technology (inter-RAT) mobility scenarios, leading to failures in EPS to 5GS single-registration idle mode and 5GS to EPS connected mode handover scenarios, which negatively impact subscriber mobility experience.
Innovation Solution
The proposed solution involves configuring the MME as a new/custom NF type within the Network Repository Function (NRF) to enable AMF to identify and retrieve MME information, facilitating context transfers between 3GPP 4G and 5G networks through NF management services and DNS-based mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current 3GPP standards are used for inter-RAT mobility management, then existing network architecture is maintained, but MME identification fails in inter-RAT mobility scenarios leading to handover failures
Solution Approach 1:
The NRF is enhanced to serve dual purposes: maintaining its existing 5G network function registration services while simultaneously providing 4G MME identification and context transfer capabilities. This allows the NRF to handle both 5G AMF registrations and 4G MME lookups through a unified interface, resolving the contradiction between maintaining existing architecture and supporting inter-RAT mobility
Solution Approach 2:
The NRF acts as an intermediary between the AMF and the MME in inter-RAT mobility scenarios. When an AMF needs to transfer user equipment context to a 4G network, it queries the NRF which then identifies and provides the appropriate MME information. This mediator role enables seamless inter-RAT handovers without requiring direct AMF-MME communication protocols
2Productivity
If MME information is stored in NRF for inter-RAT mobility, then context transfer efficiency improves, but network database complexity increases
Solution Approach 1:
MME information is pre-registered and stored in the NRF database before inter-RAT mobility events occur. This preliminary action allows the NRF to quickly retrieve and provide MME identifiers during handover scenarios without performing complex real-time calculations, thereby improving context transfer efficiency while maintaining manageable database complexity through structured pre-configured data
Data Source
AI summary
Presented herein are efficient techniques through which a Third Generation Partnership Project (3GPP) Access and Mobility Management Function (AMF) may retrieve information for a Mobility Management Entity (MME) to support graceful mobility for various inter-Radio Access Technology (inter-RAT) mobility scenarios. In one example, a method includes determining, by an AMF, an inter-RAT mobility event for a user equipment; identifying, by the AMF, an MME associated with the inter-RAT mobility event based, at least in part, on MME information contained in a network database; and transferring context information for the user equipment between the AMF and the MME. In one instance, the network database may be a Network Repository Function (NRF) for a 3GPP Fifth Generation mobile network and the MME information may be associated with an MME network function type stored in the NRF.